Overhung OH Amine pump

[mustafa2014]

Dear all good day,

I have a question regarding Amine pump, it is Overhung Single Stage Pumps.

they have problem with bearing , the voltrx plate in suction port of the pump always broken & problems with vibrations.
I think because of a high flow it is :

Q=1350 M3/H

H=70M.

I think the selection of the pump is wrong it should be BB pump. What do you think? what is the maximum capacity for OH pumps?

Do you have any reference.

 

[Artisi]

Pump detail, brand, model, speed etc. would help along with the pump curve.
Why do you think the selection is wrong?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[mustafa2014]

thanx artisi for your reply i will provide all the data .

I think the selection is wrong because the flow is too much for a single stage pump

 

[Artisi]

If the pump duty is located on the appropriate part of the H Q curve when the flow is not too high.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[1gibson]

"Flow too much for a single stage" makes no sense. If you said the head was too high for a single stage, then you might be on to something. But without seeing a curve, nobody can help you.

 

[JJPellin]

If I did the math correctly, that is probably twice the capacity of the largest amine pump we have that is an overhung configuration. So, this is certainly a very large pump. But, that does not really answer the question about the cause of your failures. I do not know what a "voltrx plate" is. If I was working on the project to install an amine pump with this flow rate and head, I would probably specify a single stage, double suction, between bearings, radial split, API pump. But, that does not necessarily mean that your pump is failing because it is too large.

Johnny Pellin

 

[mustafa2014]

dears all please find the attached pump data please your support

 

[Artisi]

Pump performance curve ???????

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[mustafa2014]

sorry please find attached the pump curve

 

[Artisi]

Without getting too academic at this point you need to look at and consider the following:

1. The pump selection for the design duty appears to be OK and the pump should operate as required, although in my opinion not a particularly good pump selection (poor efficiency, NPSH marginal)

2. However, the design head is 73m but you have advised a head of 70m - WHY? is this an accurately measured head, a guess or is it misinformation?

I suggest that the pump output (flow /head / power) is very carefully measured and the inlet conditions are very carefully looked at - NPSHr / NPSHa could be marginal.

What is the "voltrx"(vortex) plate" is it a flow straightening device in the pump inlet.

You say the pump vibrates, any vibration analysis undertaken - is it also noisy? (cavitation).

Analysing a pump problem such as this is always difficult and over the internet virtually impossible without very clear and well documented information.

Over to you for more data.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[mustafa2014]

dear Artisi, THank you very much for your reply.Please check the replies.

2- accurately measured head.
3-voltrx"(vortex) plate": is a vertical plate on the suction of the pump it seems like to break the flow coming to the pump.
4- vibration analysis undertaken: the pump is too noisy. I will send you ONE OF A CBM report (all reports have the same analyzes)

More over i have some think very useful in SHELL standard it is as following:-


NPSH The Net Positive Suction Head Required (NPSHR) shall assume that the pump is handling water; no corrections shall be made for other liquids. The Net Positive Suction Head Available (NPSHA) shall exceed the Net Positive Suction Head Required (NPSHR) by at least 1 metre throughout the range from minimum continuous stable flow up to and including the rated capacity. If the suction pressure at the pump is less than atmospheric, this margin shall be at least 2 metres. From rated capacity up to 125% of best efficiency point the NPSHR shall not exceed the NPSHA. For liquids containing dissolved gases, to avoid cavitation damage due to vapour induced flow path restrictions, NPSHA shall be 1.5 x NPSHR, with a minimum margin of 5 metres between NPSHA and NPSHR. This shall apply over the operating range, which shall not be outside 70% to 110% of BEP flow. The maximum impeller tip speed in sulfinol and carbonate service shall be 45 m/s; for these services the Manufacturer shall provide evidence of successful applications in similar duties and the Principal’s approval of pump selection is required.


Mustafa

 

[Artisi]

Mustafa
Vibration, not my field of expertise although the figure look marginally acceptable to me, I would hope that more experienced guys with vibration experience can answer for you.

Coming from a pump manufacturing background as well as hands on experience with application and trouble shooting experience I would tend to say that there is probably nothing wrong with the pump - the problem is its application.
I. you are reporting 70m head, the pump has been sized for 73m head - this could be the start of the problem - where on the curve is the pump operating -- Question?
2. from the photo with the vibration report shows what looks like a large diameter pipe up to the pump inlet - what is the pump suction diameter and what is the pipe diameter - are they the same. If the pipe is a larger diameter than the inlet, how is the transition made?
3. Have you throttled the pump discharge head to impose additional head ie., 73m - any change to vibration / noise.
4. what is the mode of failure of the vortex breaker - is it vibrating and failing due to fatigue?
5. think you need to carefully analyse the NPSHa/r component of the operation to ensure you have a sufficient margin of safety.

It appears that sometimes the vibration has been reported as fair or good and other times critical - why the difference - must be a change in operation conditions.
27/11/2014 11:27:22
FAIR
DfCnd
24.7 Hz
1482 rpm
03/11/2014 15:47:48
GOOD
DfCnd
24.7 Hz
1482 rpm
14/01/2014 17:28:44
FAIR
DfCnd
24.7 Hz
1482 rpm
27/12/2013 15:45:16
CRITICAL
DfCnd
24.7 Hz
1482 rpm
20/12/2013 11:37:25
CRITICAL
DfCnd
24.7 Hz
1482 rpm
27/03/2013 10:27:00
GOOD
DfCnd
24.7 Hz
1482 rpm

Needs looking into.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)